Other renewable energy sources Hydropower Wind energy Ocean Thermal Biomass Geothermal Tidal

Hydropower Well established electrical generation technology, about 100 years old Known for over 2000 years that the force of moving water on a water wheel could save human labor 13th century-hammers in iron works in Europe were operated with waterwheels. 16th century –primary source of industrial power in Europe In the US, mills were established at sites with reliable water flow and dams were constructed to regulate water flow. Cave mill here in BG. Several hydro powered mills for corn, flour and sawing in the 19th century existed on this site at different times. With the advent of electricity, water wheels were used to drive electricity generation. About 7% of US energy generation is from hydroelectric plants

The physics of Hydropower Gravitational potential energy in the water at a height h above the wheel is converted to kinetic energy of the wheel which drives a turbine and generates electricity. So each mass element of water, m, falls a distance h and attain a velocity v. So its initial potential energy is mgh, where g is the acceleration due to gravity (9.8m/s2) and the kinetic energy is 1/2mv2. This tells us the amount of potential energy available to be converted to kinetic energy is 9.8 joules per kilogram of water per meter of height above the wheel. h is often called the head. Efficiencies of 80-90% can be achieved. Power = (Height of Dam (distance the water falls)) x (River Flow) x (Efficiency) / 11.8 where the height is in feet, river flow is in cubic feet per second , efficiency is what you expect and 11.8 converts from feet and seconds to killowatts

Plant operation

Hydro Turbine

Net exploitable hydropower resources

Advantages No Pollution No waste heat High efficiency Plants have decades long lifetimes and low maintenance costs Good response to changing electricity demands Damming of rivers can serve other purposes: flood control, irrigation, drinking water supply

Limitations About 50% of the US capacity for Hydro is developed Limited lifetimes for certain reservoirs-as the fill with silt, they become less useful for water storage. But the dam must be maintained long term, if it fails, communities downstream are in danger from the tremendous volume of silt that would be released. Loss of free flowing streams due to damming and the loss of the lands flooded by damming a river-environmental impacts Salmon population in the Nothwest has been impacted Flood risk due to dam failures Currently hundreds thousands of people in danger if dam failures occur

Fish Ladders Solution to the salmon problem - have not been very effective